Biomarkers and molecular epidemiology in mutation/cancer research

Bulky DNA Adducts, Tobacco Smoking, Genetic Susceptibility, and Lung Cancer Risk

The generation of bulky DNA adducts consists of conjugates formed between large reactive electrophiles and DNA-binding sites. The term "bulky DNA adducts" comes from early experiments that employed a ³²P-DNA postlabeling approach. This technique has long been used to elucidate the association between adducts and carcinogen exposure in tobacco smoke studies and assess the predictive value of adducts in cancer risk. Molecular data showed increased DNA adducts in respiratory tracts of smokers vs nonsmokers. Experimental studies and meta-analysis demonstrated that the relationship between adducts and carcinogens was linear at low doses, but reached steady state at high exposure, possibly due to metabolic and DNA repair pathway saturation and increased apoptosis. Polymorphisms of metabolic and DNA repair genes can increase the effects of environmental factors and confer greater likelihood of adduct formation. Nevertheless, the central question remains as to whether bulky adducts cause human cancer. If so, lowering them would reduce cancer incidence. Pooled and meta-analysis has shown that smokers with increased adducts have increased risk of lung cancer. Adduct excess in smokers, especially in prospective longitudinal studies, supports their use as biomarkers predictive of lung cancer.

Chromosome aberrations in peripheral blood lymphocytes of Croatian hospital staff occupationally exposed to low levels of ionising radiation

Medical staff is an occupational group exposed to different agents suspected to induce genetic damage. Among them ionising radiation is the most studied. Cytogenetic analysis of human chromosomes in peripheral lymphocytes allows direct detection of mutation in somatic cells. This study investigated the cytogenetic effects of low-level ionising x-radiation in 48-hour peripheral blood lymphocyte cultures sampled from 765 hospital staff occupationally exposed to several agents known or suspected to induce chromosome damage and compared them with 200 control subjects. The exposed subjects were divided in eight (8) groups according to their specialties and job titles. The exposed groups manifested an increase in all types of chromosome aberrations. Acentric fragments were the most frequent chromosome-type aberration. Dicentric chromosomes were statistically significant only in urologists/gynaecologists. Age and smoking significantly influenced the incidence of dicentrics in the exposed groups. The frequency of ring chromosomes was low in all exposed groups (range: 0-2), and none were found in the control group. These findings indicate the importance of periodic medical checkups of hospital staff occupationally exposed to low doses of ionising radiation. The purpose is to create an individual cytogenetic register, where changes could evidence individual risks.

The effects of etodolac, nimesulid and naproxen sodium on the frequency of sister chromatid exchange after enclused third molars surgery

PURPOSE

Non-steroidal anti-inflammatory drugs (NSAID) are frequently used in oral surgical procedures in dentistry. The evaluation of the frequency of sister chromatid exchange (SCE) is accepted as a reliable cytogenetic method to assess the genotoxic effects of environmental factors.

MATERIALS AND METHODS

In this study, the genotoxic effects of various NSAIDs were assessed in 30 patients to who they were administered following encluosed third molar surgery using SCE analysis before and after the operation. The frequency of SCE was evaluated before the operation and after 3 days of etodolac, nimesulid and naproxen use.

RESULTS

There was no statistically significant difference in the frequency of SCE between the preoperative and postoperative states in patients given etodolac, nimesulid or naproxen sodium.

CONCLUSION

Short term use of selective and non-selective NSAIDs was not associated with a significant genotoxic effect that could be detected using the SCE method in peripheric lymphocytes.

The genotoxic effects in lymphocyte cultures of children treated with radiosynovectomy by using yttrium-90 citrate colloid

The aim of this study was to investigate the genotoxic effect on the peripheral blood lymphocytes potentially induced by yttrium-90 citrate colloid (Y-90) in children who were undergoing radiosynovectomy for hemophilic synovitis, using chromosomal aberration analysis (CA) and the micronuclei (MN) assay for detecting chromosomal aberrations, as well as the sister chromatid exchanges (SCE) technique for assessed DNA damage.

MATERIALS AND METHODS

Cytogenetic analyses were undertaken in 18 boys (mean age, 14.5 +/- 2.1 years) with hemophilic synovitis who underwent radiosynovectomy with Y-90. CA, MN, and SCE were evaluated just prior to, then at 2 and 90 days following radiosynovectomy from the peripheral lymphocytes of the children. An activity of 185 MBq of Y-90 was injected into the 18 knee joints under aseptic conditions. To check the possibility of leakage from the joint and its migration within the body, the patients underwent scanning under a dual-headed gamma camera at the hours 2 and 48 following the procedure.

RESULTS

The procedure was well tolerated in all the children, and there was no extra-articular activity owing to extra-articular leakage of radioactive material in whole-body imaging. The mean frequency of CA in lymphocytes determined prior to the onset of therapy (0.31 +/- 0.48/900 cells) was not significantly increased, in comparison to the control values obtained 2 (0.30 +/- 0.48/900 cells) and 90 days (0.15 +/- 0.37/900 cells) after radiosynovectomy (p = 1.0 and 0.625, respectively). We observed that MN frequency was mildly increased in lymphocytes 2 days after therapy (8.30 +/- 1.89 MN/1000 binucleated cells vs. 9.23 +/- 1.79 MN/1000 binucleated cells; p = 0.013). But there was no significant difference between the baseline and the day 90 control levels of MN (p = 0.196). In the analysis of SCE frequency, there were no significant differences between the baseline (8.11 +/- 0.77) and the control analysis performed 2 and 90 days following radiosynovectomy (8.18 +/- 0.77 and 8.07 +/- 0.74; p = 0.710 and 0.662, respectively).

CONCLUSIONS

The results of this study indicated that high radiation doses are not obtained by peripheral lymphocytes of children who undergo Y-90 radiosynovectomy and, therefore, they contradict a high cancer risk.

Monitoring the genotoxic effects of radiosynovectomy with Re-186 in paediatric age group undergoing therapy for haemophilic synovitis

PURPOSE

The aim of this study was to investigate the genotoxic effect on the peripheral blood lymphocytes potentially induced by Re-186 in paediatric age group undergoing radiosynovectomy for haemophilic synovitis, by using chromosomal aberration analysis (CA) and the micronuclei (MN) assay for detecting chromosomal aberrations, as well as the sister chromatid exchanges (SCE) technique for assessing DNA damage.

METHODS

Cytogenetic analyses were evaluated in 20 boys (mean age: 13.8 +/- 2.7 years) before, and 2 and 90 days after radiosynovectomy from the peripheral lymphocytes of the patients. Joint retention and extra-articular spread of the radionuclides were evaluated by using quantitative gamma camera imaging.

RESULTS

Imaging after radiosynovectomy revealed local lymph node visualization in 8 (40%) patients and hepatosplenic visualization in 3 (15%) patients due to extra-articular leakage of radioactive material. The mean frequency of chromosome aberrations (0.2 +/- 0.4/1000 cells) determined prior to the onset of therapy was not significantly increased in comparison with control values obtained 2 days (0.4 +/- 0.5/1000 cells) and 90 days (0.2 +/- 0.4/1000 cells) after therapy (P = 0.754 and P = 1.0). In the analysis of MN and SCE, when we compare the baseline levels, the mean MN and SCE frequencies were slightly higher in the control analyses performed 2 and 90 days after radiosynovectomy but there were no significant differences between baseline and control levels (chi(2) = 2.621, P = 0.270 and F = 0.573, P = 0.569, respectively).

CONCLUSION

The major finding of this study with relatively small sample is that, radiosynovectomy with Re-186 does not seem to induce early genotoxic effects on the peripheral blood lymphocytes in paediatric age group.

Use of whole blood directly for single-cell gel electrophoresis (comet) assay in vivo and white blood cells for in vitro assay

The present study investigated the use of whole blood from humans and rats directly for single-cell gel electrophoresis (comet) assay. As little as 20 microl of whole blood was sufficient for comet assay, and the comet images obtained from whole blood were not different from those obtained from isolated lymphocytes. The DNA remained intact up to 4 h at 4 degrees C after isolation and had no observable strand breakage, when whole blood was cryopreserved (at -80 degrees C) in 10% pre-cooled DMSO up to 60 days. To demonstrate that the whole-blood technique could be applied to in vivo studies, we injected rats with a known carcinogen Fe/NTA and measured DNA strand breaks in whole blood in comparison with isolated lymphocytes. We showed that Fe/NTA injection resulted in similar extent of DNA strand breakage in both whole blood and lymphocytes, indicating that whole-blood method can be used for in vivo genotoxic studies. One disadvantage of the whole-blood technique is that whole blood cannot be used for in vitro studies because of the interferences from red blood cell (RBC) components. However, this problem can be overcome by prior hemolysis of RBCs and a brief centrifugation to obtain white blood cells (WBCs), which can then be used for in vitro incubation with genotoxic compounds before comet assay. Overall, this whole-blood technique for comet assay is expected to provide a simple, rapid, and cost-effective alternative for the existing comet assay using isolated lymphocytes in situations such as when time and cost are limiting factors.

A molecular epidemiological approach to health risk assessment of urban air pollution

The ambient air of urban centres is polluted with potentially toxic chemicals mostly arising from the combustion or fuels used for transport. Among these compounds, benzene raises particular concern due to its haematoxicity and leukaemogenic risks. Although limits of benzene in air have been established in the European Union (5 microg/m(3)), individual exposure levels--and therefore risk estimates--cannot merely be extrapolated from environmental concentrations. Molecular epidemiology can facilitate health risk assessment by investigating the relationship between exposure to environmental pollutants and quantification of biomarkers that lie on the pathway of carcinogenesis upstream of clinical disease. We review the available for biomarker studies regarding health risks linked to environmental benzene exposure, and make some suggestions for future work.

Biological sample collection and processing for molecular epidemiological studies

Molecular epidemiology uses biomarkers and advanced technology to refine the investigation of the relationship between environmental exposures and diseases in humans. It requires careful handling and storage of precious biological samples with the goals of obtaining a large amount of information from limited samples, and minimizing future research costs by use of banked samples. Many factors, such as tissue type, time of collection, containers used, preservatives and other additives, transport means and length of transit time, affect the quality of the samples and the stability of biomarkers and must be considered at the initial collection stage. An efficient study design includes provisions for further processing of the original samples, such as cryopreservation of isolated cells, purification of DNA and RNA, and preparation of specimens for cytogenetic, immunological and biochemical analyses. Given the multiple uses of the samples in molecular epidemiology studies, appropriate informed consent must be obtained from the study subjects prior to sample collection. Use of barcoding and electronic databases allow more efficient management of large sample banks. Development of standard operating procedures and quality control plans is a safeguard of the samples' quality and of the validity of the analyses results. Finally, specific state, federal and international regulations are in place regarding research with human samples, governing areas including custody, safety of handling, and transport of human samples, as well as communication of study results.Here, we focus on the factors affecting the quality and the potential future use of biological samples and some of the provisions that must be made during collection, processing, and storage of samples, based on our experience in the Superfund Basic Research Program and Children's Environmental Health Center, at the University of California, Berkeley.

Genotoxicity of hyperbaric oxygen

Hyperbaric oxygen (HBO) treatment is applied as a therapy for a wide variety of diseases with symptoms caused by lack of oxygen in the target tissues. However, it is known that exposure to high concentrations of oxygen may lead to oxidative stress and cause cell and tissue damage. Oxygen toxicity and possible cancer-promoting effects of HBO therapy have been a matter of serious concern. Although a cancer-inducing effect of HBO was not found to date, recent studies clearly indicated an induction of oxidative DNA damage in blood cells of healthy subjects after HBO under therapeutic conditions. The biological significance of this finding has been investigated in a series of in vitro and in vivo tests. This review summarizes these studies and critically discusses potential adverse genetic effects of HBO therapy. Furthermore, since an induction of anti-oxidative defense mechanisms has been determined after HBO exposure, a modified treatment regimen of HBO therapy is proposed which avoids genotoxic effects.

Gender-related differences in basal DNA damage in lymphocytes of a healthy Indian population using the alkaline Comet assay

The Comet assay, a sensitive, rapid and non-invasive technique, measures DNA damage in individual cells and has found wide acceptance in epidemiological and biomonitoring studies to determine the DNA damage resulting from lifestyle, occupational and environmental exposure. The present study was undertaken to measure the basal level of DNA damage in a normal, healthy Indian male and female population. Out of the 230 volunteers included in this study, 124 were male and 106 were female. All the individuals belonged to a comparable socio-economic background and aged between 20 and 30 years. They were also matched for their smoking and dietary habits. The period of sample collection was also matched. The results revealed a statistically significant higher level of DNA damage in males when compared to females as evident by an increase in the Olive tail moment [3.76+/-1.21 (arbitrary units) for males as compared to 3.37+/-1.47 for females (P<0.05)], tail DNA (%) [10.2+/-2.96 for males as compared to 9.40+/-2.83 for females (P<0.05)] and tail length (microm) [59.65+/-9.23 for males and 49.57+/-14.68 for females (P<0.001)]. To our knowledge, this report has, for the first time demonstrated significant differences in the basal level of DNA damage between males and females in a normal healthy Indian population.

Assessment of genotoxic damage in nurses occupationally exposed to antineoplastics by the analysis of chromosomal aberrations

To estimate the genotoxic risk of occupational exposure to antineoplastic drugs, chromosomal aberration (CAs) frequencies in peripheral lymphocytes were determined for 20 nurses handling antineoplastics and 18 referents matched for age and sex. Urinary cyclophosphamide (CP) excretion rates, which are used as a marker for drug handling, were also measured on these nurses. We have observed significant frequencies of CAs (about 2.5-fold increase) including chromatid breaks, gaps, and acentric fragments for nurses handling antineoplastics as compared to control subjects (p < 0.05, p < 0.01, excluding and including gaps, respectively). The mean value of CP excretion rate for 12 nurses was 1.63 microg/24 h, suggesting that when the nurses handled CP (and other antineoplastic drugs) this particular compound was absorbed. Our study has shown that increased genetic damage was evident in nurses, at population level, due to occupational exposure to antineoplastics. Until the effects of handling antineoplastics from low-level exposure are known, it will be important to keep the exposure to a minimum.

Biomarkers to assess the genetic damage induced by alcohol abuse in human lymphocytes

Alcohol abuse is a major risk factor for cancer of the upper alimentary tract, the upper respiratory tract, and liver. Chromosome damage is used as early effect biomarker in the surveillance of human exposure to genotoxic carcinogens. In the present study, two genetic markers, namely chromosome aberrations (CAs) and micronuclei (MN), were used to evaluate genetic damage in peripheral lymphocytes from 20 alcoholics, 20 abstinent alcoholics, and 20 controls. Composition of the three groups was fairly similar as regards sex, age and smoking habits. A highly significant increase was observed in the frequencies of CA and MN in lymphocytes of alcoholics as compared both with controls and abstinent alcoholics. However, no correlation was found between the length of alcohol abuse and the frequencies of either biomarkers in alcoholics. CA and MN frequencies in abstinent alcoholics were similar than those in controls. Our data indicate that CA and MN can be two useful biomarkers to assess genetic damage associated with alcohol abuse. They could be included in programs for cancer prevention in alcoholics. Abstinence appears to normalize the frequency of both MN and CA. This could offer therapists another tool to help alcoholics change their lifestyle.

Methods of in vitro toxicology

In vitro methods are common and widely used for screening and ranking chemicals, and have also been taken into account sporadically for risk assessment purposes in the case of food additives. However, the range of food-associated compounds amenable to in vitro toxicology is considered much broader, comprising not only natural ingredients, including those from food preparation, but also compounds formed endogenously after exposure, permissible/authorised chemicals including additives, residues, supplements, chemicals from processing and packaging and contaminants. A major promise of in vitro systems is to obtain mechanism-derived information that is considered pivotal for adequate risk assessment. This paper critically reviews the entire process of risk assessment by in vitro toxicology, encompassing ongoing and future developments, with major emphasis on cytotoxicity, cellular responses, toxicokinetics, modelling, metabolism, cancer-related endpoints, developmental toxicity, prediction of allergenicity, and finally, development and application of biomarkers. It describes in depth the use of in vitro methods in strategies for characterising and predicting hazards to the human. Major weaknesses and strengths of these assay systems are addressed, together with some key issues concerning major research priorities to improve hazard identification and characterisation of food-associated chemicals.

Biomarkers in disease and health

Biomarkers have considerable potential in aiding the understanding of the relationship between diet and disease or health. However, to assess the role, relevance and importance of biomarkers on a case by case basis it is essential to understand and prioritise the principal diet and health issues. In the majority of cases, dietary compounds are only weakly biologically active in the short term, have multiple targets and can be both beneficial and deleterious. This poses particular problems in determining the net effect of types of foods on health. In principle, a biomarker should be able to contribute to this debate by allowing the measurement of exposure and by acting as an indicator either of a deleterious or of an enhanced health effect prior to the final outcome. In this review, the examples chosen - cancer (stomach, colon/rectal, breast); coronary heart disease and osteoporosis - reflect three major diet-related disease issues. In each case the onset of the disease has a genetic determinant which may be exacerbated or delayed by diet. Perhaps the most important factor is that in each case the disease, once manifest, is difficult to influence in a positive way by diet alone. This then suggests that the emphasis for biomarker studies should focus on predictive biomarkers which can be used to help in the development of dietary strategies which will minimise the risk and be of greater benefit.

The effect of the genetic polymorphisms of CYP1A1,CYP2D6, GSTM1 and GSTP1 on aromatic DNA adduct levels in the population of healthy women

Aromatic DNA adduct levels and polymorphisms of two phase I enzymes - CYP1A1 and CYP2D6 and two phase II enzymes - GSTM1 and GSTP1 were analyzed in a group of 133 nonsmoking healthy women 35-45 years old and holding jobs not connected with the exposure to the combustion products of organic matter. They were office workers from the south and north-eastern parts of Poland. Blood samples were collected in winter and in summer. Aromatic DNA adduct levels were measured in all winter and summer samples. The frequencies of CYP1A1, CYP2D6, GSTM1 and GSTP1 polymorphisms in samples from the studied women did not show any differences when compared with other Caucasian populations and the Polish male population studied previously. The differences in the levels of DNA adducts among the carriers of different genotypes were statistically non-significant. Analysis of combined genotypes selected the groups of volunteers with the highest and the lowest DNA adduct levels. The highest levels of DNA adducts were observed in the carriers of GSTM1(null)/CYP1A1Ile/Val (8.00+/-13.00 adducts/10(8) nucleotides in summer samples) and GSTP1-AA/CYP1A1Ile/Val genotypes (7.00+/-4.32 in winter and 7.30+/-7. 27/10(8) nucleotides in summer). The lowest levels of DNA adducts (3. 00+/-2.30 in winter and 2.00+/-3.16/10(8) nucleotides in summer) were found in the carriers of the genotype GSTP1-AG+GG/CYP1A1Ile/Val. The levels of DNA adducts in these groups were determined by the polymorphisms of GSTM1 and GSTP1 phase II detoxifying enzymes.

Single cell gel electrophoresis assay: a new technique for human biomonitoring studies

Human biomonitoring using the single cell gel electrophoresis (SCGE) or comet assay is a novel approach for the assessment of genetic damage in exposed populations. This assay enables the detection of various forms of DNA damage in individual cells with ease and speed and is, therefore, well suited to the analysis of a large group in a population. Here, application of SCGE assay in the identification of dietary protective factors, in clinical studies and in monitoring the risk of DNA damage resulting from occupational, environmental or lifestyle exposures is reviewed. Also, the comparative sensitivity of SCGE assay and conventional cytogenetic tests to detect genetic damage is discussed. Finally, strengths and shortcomings of the SCGE assay are addressed.

Functional foods: the US perspective

Widespread interest in the possibility that selected foods might promote health has resulted in the coining of the term functional food, although agreement about what is and what is not a functional food is lacking. Public interest in functional foods is increasing because of higher health care costs; the passage of federal legislation affecting many food categories, including the expanded category of dietary supplements; and recent scientific discoveries linking dietary habits with the development of many diseases, including coronary heart disease and some cancers. A variety of foods have been proposed as providing health benefits by altering one or more physiologic processes. Biomarkers are needed to assess the ability of functional foods or their bioactive components to modify disease and to evaluate the ability of these foods to promote health, growth, and well-being. Evidence suggests that several biomarkers may be useful for distinguishing between diseased and nondiseased states and even for predicting future susceptibility to disease. A variety of biomarkers will probably be needed to develop a profile for an individual that reflects the impact of diet on performance and health. Another area of interest is the interaction of nutrients and their association with genetics. These interactions may account for the inconsistent interrelations observed between specific dietary constituents and the incidence of disease. Greater understanding of how diet influences a person's genetic potential, overall performance, and susceptibility to disease can have enormous implications for society. As new discoveries are made in this area, consumers will need access to this information so that they can make informed decisions.

Mutation induction by different types of radiation at the Hprt locus

Mutation induction at the Hprt locus in Chinese hamster cells was studied after exposure to ultraviolet light, X-rays and alpha particles. While mutant frequency as a function of dose or fluence followed a linear-quadratic relationship with UV and X-rays, it showed a linear dependence for alpha particles. If mutant frequency is plotted vs. the logarithm of surviving fraction, a linear relationship is found in all cases although with different slopes. These are about equal with the two types of ionising radiations but about 10 times larger for UV. They can be used as a measure of mutagenic potential and are termed mutagenicity. It is shown that this parameter is correlated with the maximum of mutant yield, i.e., the number of mutants per cell at risk. It is concluded from this analysis that the maximum mutant yield is always found at doses or fluences which lead to 37% survival irrespective of the kind of radiation. If mutation induction is measured in X-irradiated cells after pre-exposure to UV, mutant frequency is higher than expected on the basis of independent action of the two radiations. Deletion spectra were determined by using multiplex polymerase chain reaction. It was found that the background of spontaneous mutants varied considerably and showed frequently repetitive patterns, presumably because of clonal expansion of pre-formed mutants. UV-induced mutants did not contain any deletions, while those with both X-rays and alpha particles the majority displayed partial and total deletions. Based on a total number of 134 X-ray- and 192 alpha-induced mutants, it is concluded that the total fraction of mutant clones without deletions (partial or total) is about 40% for X-rays and only about 20% for alpha-particles.

Population monitoring: experience with residents exposed to uranium mining/milling waste

More emphasis should be placed upon using biomarkers to address potential health risk among populations exposed to high concentrations of environmental toxicants. Among these studies, those which integrate exposure measurements with analyses of validated biomarkers may provide more reliable information for risk assessment and disease prevention. We have used a multidisciplinary approach to elucidate potential health hazards in a population living around uranium mining/milling facilities. The study included 24 target and 24 control residents who were matched for age and gender and selected based on time of residence in the study areas and proximity to mining/milling sites. Environmental samples were analyzed for uranium-238 (238U) concentrations and lead isotope ratios using inductively coupled plasma-mass spectrometry (ICP-MS) procedures, and blood samples were collected for cytogenetic analysis. We found that the 238U concentrations in soil samples were significantly higher than those in the control areas. In addition, the concentrations in the surface soil were significantly higher than in the subsurface soil (p<0.05) from target areas indicating environmental contamination by the mining/milling activities. Lead isotope data from soil samples taken near a railroad transfer location was significantly different from those of other sites, indicating contamination by non-native ore transported from sources outside of the region to local milling facilities for processing. Therefore, local residents have been exposed to low levels of radioactive contamination from the mining/milling activities on a daily basis for many years. From our cytogenetic analysis, the target population had more chromosome aberrations than the controls, although the differences were not significant (p<0.05). However, using our challenge assay, cells from the target population had a significantly abnormal DNA repair response, compared to cells from the same control population. In conclusion, the observed environmental contamination by uranium is consistent with the observed genotoxic effects in the target residents. Therefore, the residents have increased health risk and some of the health problems will most likely be related to exposure to the radioactive contaminants. Since the chromosome aberration frequency revealed increased, but not significant differences between the exposed and the control populations, we conclude that the health risk among the exposed residents is similar to those among nuclear workers.

Cytogenetic monitoring in coke oven workers

Cytogenetic markers (chromosomal aberrations, sister chromatid exchanges (SCE), cells with high frequency of SCE (HFC), the heterogeneity index SCE (SCE-H) and genetic polymorphism of genotypes GSTM1 and NAT2 were evaluated in the peripheral lymphocytes of 64 coke oven workers and 34 control subjects from the same plant. Personal monitors were used to evaluate exposure to eight carcinogenic (polycyclic aromatic hydrocarbons) PAHs, including B[a]P, during an 8-h working shift. Smoking habits were checked by urinary cotinine measurement. The exposure among coke oven workers ranged widely from 0.6 to 547 microgram/m3 and 2 to 50 137 ng/m3, for carcinogenic PAHs and B[a]P, respectively. The respective values in controls were 0.07 to 1.51 microgram/m3 and from 2 to 63 ng/m3. The results of biomonitoring in exposed vs. control subjects were as follows: frequency of chromosomal aberrations (% AB.C.), 2. 30% AB.C. vs. 1.09% AB.C. (P<0.05); sister chromatid exchanges, 7.47 SCE/cell vs. 5.49 SCE/cell (P<0.05); HFC, 5.94% vs. 2.06% (P<0.05) and SCE-H index, 1.49 vs. 1.01 (P<0.05). All the cytogenetic markers were significantly increased in the exposed vs. control groups. The effect of smoking was observed only in SCE when evaluated as HFC. Using individual exposure data for carcinogenic PAHs, a significant correlation between exposure and %AB.C. (r=0.372, P=0.0002), SCE/cell (r=0.331, P=0.001), HFC (r=0.467, P=0.007) and SCE/H (r=0. 286, P=0.004) was found. No effects of GSTM1 and NAT2 genotypes, individually or in combination, on the cytogenetic markers was observed. It is concluded that occupational exposure of coke oven workers involved in this study resulted in an increased level of chromosomal aberrations and SCE. The frequency of AB.C. and SCE/cell was found to be related to exposure to carcinogenic PAHs.

Erythrocyte as a potential model for study of lifelong somatic mutations

The detection and measurement of somatic cell mutation in vivo is an important subject of research for the assessment of human cancer risk induced by various environmental genotoxic factors. The possible mechanisms which influence the persistence of mutant cells of the hematoimmune system in the peripheral blood are presented. The erythroid system is a system which accumulates mutational lesions and so stably generates red blood cells with various phenotypic changes.

Comparative biomonitoring study of workers at a waste disposal site using cytogenetic tests and the comet (single-cell gel) assay

Workers exposed to environmental pollutants at a waste disposal site were studied for genotoxic effects with cytogenetic tests and the comet (alkaline single-cell gel) assay. Analyses were performed on peripheral blood samples of 44 workers at a waste disposal site (DM) and 47 subjects of a control group (VE) matched for gender, age, and smoking habits. Chromosomal aberrations were evaluated in 1,000 lymphocytes per individual, sister chromatid exchanges in 50 cells, and DNA migration (tail moment) was determined in 100 leukocytes. Structural chromosome aberrations were more frequent in DM than in VE, but only the frequency of acentric fragments and the percentage of aberrant cells (excluding gaps) was significantly increased. No significant difference was found for the mean frequency of SCE. A statistically significant difference was also seen with the comet assay. The mean tail moment was higher in DM than in VE. However, no correlation was found between cytogenetic data and the effects in the comet assay. The results of our study indicate that DNA effects in the comet assay represent an independent endpoint which might be useful for the biomonitoring of genotoxic effects in addition to established tests.

Development of a mouse model for studying in vivo T-cell receptor mutations

An experimental system was established to study in vivo T-cell receptor alpha beta (TCR) mutations in murine CD4+ T-lymphocytes. The frequency of TCR-defective mutant T-cells that have the CD3-4+ surface phenotype, was measured using two-color flow cytometry of splenic T-cells passed through nylon wool. The spontaneous TCR mutant frequency (MF) in BALB/c mice (2.3 x 10(-4)) was significantly lower than the frequencies of C57BL/6 (4.0 x 10(-4)) and C3H/He (4.2 x 10(-4)) mice. The general trend of the TCR MF started to increase at 3 days after whole-body X-irradiation, reached a peak level at 2-3 weeks, and then gradually decreased with a half-life of about 2 weeks. To analyze how the dose responses for each strain of mouse differed 2 weeks after X-irradiation, the TCR MF dose responses were fitted to a linear-quadratic or a quadratic curve. The coefficients of the quadratic terms in both models for BALB/c mice were significantly higher than those for the other two strains. These findings suggest that some genetic factor(s) may control the susceptibility of somatic genes to both spontaneous and radiation-induced mutagenesis. Establishing an animal model for in vivo TCR mutations will contribute to the clarification of certain unresolved aspects of TCR mutagenesis in humans and will further advance knowledge of screening for environmental mutagens.

A comparative investigation of DNA adducts, DNA strand breaks and gene mutations induced by benzo[a]pyrene and (+/-)-anti-benzo[a]pyrene-7,8-diol 9,10-oxide in cultured human cells

Genotoxic effects of benzo[a]pyrene (BP) and its reactive metabolites (+/-)-anti-benzo[a]pyrene-7,8-diol 9,10-oxide ((+/-)-anti-BPDE) were comparatively investigated in vitro with the permanent human fibroblast cell line MRC5CV1. Induced DNA adducts were measured by 32P-postlabeling, DNA strand breakage was determined by the comet assay and the HPRT gene mutation test was used to detect cytotoxicity and mutagenicity. Treatment of MRC5CV1 cells with S9 mix-activated BP or with (+/-)-anti-BPDE resulted in a concentration-dependent increase in DNA adducts and strand breaks. Genotoxic effects of BP and (+/-)-anti-BPDE were detected by 32P-postlabeling and the comet assay with similar sensitivity. However, under the same experimental conditions, a clear induction of gene mutations was only found after (+/-)-anti-BPDE treatment. The relationship between the induction of primary DNA alterations like DNA strand breaks and DNA adducts and the induction of gene mutations is discussed.